Aging of red blood cells and impaired erythropoiesis following prolonged administration of dichloromethylene diphosphonate containing liposomes in rats
Eur J Haematol 2005: 75: 406–416. © Blackwell Munksgaard 2005. Abstract:
Objectives: To investigate whether macrophage-depleted rats may serve as a model for studying red blood cell (RBC) aging. Methods: Rats were macrophage-depleted by 4 weekly injections of dichloromethylene diphosphonate-containing liposomes (Cl2MDP-CL). The macrophage content of spleens and bone marrows (BMs) was investigated by immunohistochemistry and light microscopy and by flow cytometry, respectively, after staining with macrophage-specific monoclonal antibodies. In addition, the ultrastructure of residual BM macrophages and their ability to phagocytose zymosan was studied. BM was also studied for apoptosis (by the TUNEL reaction) and for erythroid progenitor cell content. Furthermore, RBC indices, morphology, life span (by 51Cr labeling) and aging features (MCV, density, 4.1a/4.1b membrane protein ratio, anti-spectrin IgG binding, microvesiculation) were investigated. Serum TNF-α, iron, total iron-binding capacity (TIBC) and ferritin were also determined. Results: Prolonged treatment with Cl2MDP-CL caused an almost complete depletion of macrophages in the spleen and a 58% reduction of those in the BM; the residual BM macrophages were activated as judged by their ultrastructure and phagocytic capacity in vitro. These alterations were accompanied by an increase in RBC life span and age-related RBC changes, as well as by mild anemia associated with a reduced reticulocyte count, reduced BM erythroid progenitors, increased numbers of apoptotic cells in the BM, low serum iron, high TIBC and increased serum TNF-α levels. Conclusions: Rats subjected to prolonged macrophage depletion showed an increased prevalence of senescent RBC in the circulation due to their impaired clearance by macrophages. Hence, these animals provide a model system in which mechanisms of RBC aging can be delineated. They also showed impaired erythropoiesis, presumably related to a reduction in BM macrophages and increased production of proinflammatory cytokines by residual activated marrow macrophages and other cells.
Document Type: Research Article
Affiliations: 1: Department of Experimental and Diagnostic Medicine, Section of General Pathology, University of Ferrara, Ferrara, Italy 2: Department of Biochemistry and Molecular Biology, University of Ferrara, Ferrara, Italy 3: Laboratory Division, S. Anna Hospital, Ferrara, Italy 4: Department of Haematology, Faculty of Medicine, Imperial College, London, UK
Publication date: November 1, 2005